Our group is studying the molecular mechanisms of: (a) bacteriophage lambda head assembly and (b) genetic recombination catalysed in vitro by bacteriophage T7 extracts. During the coming year we are proposing the following experiments: (a) We plan to further characterize the molecular properties of the lambda ter enzyme to learn specifically if the Nu1 protein is a subunit of this enzyme and to elucidate how the ATPase associated with the enzyme functions during DNA packaging. We are extending our studies of in vitro lambda prohead assembly by fractionating infected-cell extracts on DEAE columns. The aim is to determine the pathway of prohead assembly in vitro. (b) The mechanism of action of the T7 DNA binding protein in genetic recombination and in stimulation of the activity of the T7 exonuclease will be explored. Recombinational intermediates formed after incubation of T7 DNA with infected-cell extracts will be studied by physical and chemical means.